This invention relates to nozzles, and more particularly to a rotary nozzle suitable for distributing a stream of fire-extinguishing compressed-air foam, sufficient to extinguish or control a fire in the path of the foam stream.
In the art of firefighting, it is known to use foam produced from a solution of a foam concentrate in water. The volume of the solution is expanded by the addition of air and mechanical energy to form a bubble. structure resembling shaving cream. The bubble suffocates and cools the fire and protects adjacent structures from exposure to radiant heat. Foam is well known of being very efficient on fire fed from a liquid (oil or chemicals).
Foam can be generated using an air-aspirating nozzle, which entrains air into the solution and agitates the mixture producing bubbles of non-uniform size. With an aspirating system, the foam is formed at the nozzle using the energy of the solution stream.
Foam can also be generated by injecting air under pressure into the solution stream. The solution and air mixture are scrubbed by the hose (or pipe) to form a foam of uniform bubble size. The energy used in this system comes from the solution stream and the air injection stream. This system produces a so-called xe2x80x9ccompressed-air foamxe2x80x9d (CAF) which is capable of delivering the foam with a greater force than a comparable aspirated system described above. Foam generation for fixed pipe system is documented in the proceedings from the xe2x80x9cFire Suppression and Detection Research Application Symposiumxe2x80x9d entitled xe2x80x9cA Newly-Developed Fixed Pipe Compressed Air Foam Suppression Systemxe2x80x9d by Andrew K. Kim and George P. Crampton. This document is herein incorporated by reference.
When delivered from a hose, CAF is ejected as a xe2x80x9cropexe2x80x9d of foam with a high forward momentum through a smooth bore nozzle. An attempt to widen the delivery angle using a conventional nozzle (such as e.g. a water sprinkler) results in collapsing the bubble structure of the foam and degenerating the foam back into a solution and air.
A published Canadian patent application No. 2,131,109 describes a foam nozzle having a stationary barrel and a rotary distributor with three tubular angled outlets. The design of the nozzle is such that the combined cross-sectional areas of the outlets are not less than the cross-sectional area of the barrel and not larger than twice the cross-sectional area of the barrel.
While the nozzle of the above application is useful, there is still need for a nozzle affording higher efficiency, lower profile, larger ground coverage and a more reliable rotational arrangement or bearing.
The present invention achieves the distribution of a stream of fire-extinguishing compressed-air-foam in large circle area by using a nozzle comprising:
a supply tubing for supplying foam from a supply conduit, having a longitudinal axis;
a barrel being rotatably attached to the supply tubing and defining a passageway therein, the passageway of the barrel being at angle to the longitudinal axis of the supply tubing;
the barrel having at least one orifice which, upon forced flow of the foam, delivers a stream of the foam along a trajectory having a component that is tangential to a circular path coaxial with the longitudinal axis of the supply tubing such as to cause a rotational movement of the barrel;
the sum of all the cross-sectional areas of the at least one orifice is not less than xc2xd of the cross-section of the supply conduit.
The distribution of a stream of fire-extinguishing compressed-air-foam in large circle area can also be achieve by using a nozzle comprising:
a supply conduit for supplying foam having a longitudinal axis and a central enlarged portion;
a diffuser in flow continuity with the supply conduit having curved cross-section;
an impeller which rotates, upon forced flow of the foam, to drive an input shaft of a reducer;
an output shaft of the reducer drives the diffuser to impart a rotational movement, therefore delivering a stream of foam in a circular path coaxial with the longitudinal axis.
The present invention provides a simplified nozzle structure allowing for durability and readiness for sporadic uses.